Most absorbent articles, especially feminine pads, sanitary napkins, pantiliners, incontinent garments and the like, which are manufactured today are long and narrow and usually are relatively flat. These flat products are designed to be worn tightly against the curved torso of a human body and are generally held in place by an undergarment. Such flat products have a tendency to buckle or wrinkle as they conform to the body profile as the undergarment is pulled up and secured around the wearer's torso. These buckles and wrinkles can facilitate side leakage of body fluids which have been deposited onto the cover of the product. Side leakage is probably the number one reason way these types of absorbent articles fail.
In most instances, fluid leakage results not from saturation of the absorbent material but rather from fluid running off of the cover material. It is common for body fluid deposited onto the cover to form a pool before it penetrates down through the fluid permeable cover and into the absorbent. This pooling effect is due to a variety of factors, such as the size openings in the cover, the fluid permeability of the cover material, the amount of fluid discharged onto the cover in a short period of time, as well as the composition of the fluid itself. Body fluid may contain menses, blood, urine and other aqueous fluids. Menses, in particular, is a complex fluid which may be highly viscous and normally contains a mucoidal fraction, as well as cellular debris, amongst other aqueous components. Both the mucoidal fraction and the cellular debris tend to collect at the surface capillaries of the cover material and block the passage of the more aqueous components into the absorbent.
Side leakage occurs when the deposited body fluid pools on the cover material and is allowed to spread along the surface of the cover before being absorbed into the absorbent. Body movement and wrinkles in the product commonly assist the fluid in flowing outwardly. Since the side edges are closer to the fluid discharge area then are the distal ends, the product tends to leak at the side edges rather than at the ends. Such side leakage usually occurs well before the bulk of the absorbent has been wetted or insulted.
Attempts have been made to increase comfort of feminine care products as well as to insure greater surface contact in the perineal area by providing products having an hourglass shape. U.S. Pat. Nos. 3,805,790 and 4,490,147 teach two different hourglass shapes. An hourglass shaped product conforms better to the shape of the human thighs, especially adjacent to the perineal area. U.S. Pat. No. 4,324,246 shows an absorbent article with a seam formed inward of the outer peripheral edge along with a narrow central portion to provide a better fit with the body. A better fit means less distortion during body movement and should create a better interface between the perineal area and the cover.
Various attempts at producing a feminine product with side flaps or walls have also been tried. Examples include EPA 0,091,412 which teaches a sanitary napkin which utilizes a thicker and wider absorbent in the central portion but which also uses elastic to form upstanding walls. U.S. Pat. Nos. 4,579,556 and 4,668,230 teach arcuate shaped products having a rectangular absorbent and elastic secured to either a portion of or along the entire length of the longitudinal edges. The elastic forms upstanding walls which assist in preventing side leakage of body fluid. Two additional U.S. Pat. Nos. 4,701,177 and 4,770,657 teach three-dimensional shaped feminine pads having elasticized edges and an overall concave shape to better fit the female body. These last two patents are assigned to the present assignee and were filed after the date of the parent case to which this application depends.
Diapers represent another type of absorbent article which have experimented with leg elastics. Several U.S. Pat. Nos. which teach the use of elastic to form a body seal include: 3,860,003; 4,324,245; 4,326,528; 4,337,771; 4,352,355 and 4,496,360. It should be noted that diapers are different from feminine care products in that they do not require the same intimate contact between the wearer's body and the product itself. However, the use of elastic to form side seals is relevant to both types of products.
Now an absorbent article has been developed which has a cup-shaped configuration so as to prevent side leakage of body fluid and better conform to the curve shape of a human torso.